1. Field of the Invention
The present invention relates to a test circuit of a base station for use of a mobile radio communication system; and, more particularly, to a test circuit of a base station for testing therein a call, a hand over, a reception sensitivity of a base station, a voltage standing-wave ratio etc.
2. Discussion of Related Art
In general, it is carried out in a base station of a mobile radio communication system a call test for clarifying whether or not a call is normally effected by using an antenna of a specific sector, a hand over test for confirming whether or not the call effected in the specific sector is transferred to another sector and the transferred call is continued, a reception sensitivity test of the base station for measuring a minimum reception level of the base station, and a test for measuring a voltage standing-wave ratio (VSWR) of the antenna, the minimum reception level being for normally effectuating the call.
FIG. 1 shows a termination of a general antenna. Referring to FIG. 1, there are constructed a directional coupler 2 and an antenna 1, wherein the directional coupler 2 includes a forward port 3 and a reverse port 4 and is coupled with a test circuit of a base station in a mobile radio communication system in order for a call testing, and the antenna 1 radiates a transmission signal and absorbs a reception signal.
FIG. 2 sets forth a block diagram illustrating a test circuit of a base station for use of a conventional mobile radio communication system. In the conventional mobile radio communication system, the test circuit of base station is concerned with three sector base station. That is, each of three sectors equips one transmitting antenna and two receiving antennae.
There is provided in FIG. 2 the construction of a base station test circuit for use of a conventional mobile radio communication system. Describing the construction, the test circuit includes a tri-state switch 18-1 to 18-3 coupled with the directional coupler 2 of transmitting alpha, beta and gamma antennae, for selecting a forward path and a reverse path in a transmission step; a three path coupler 15 connected with the tri-state switch 18-1 to 18-3, for joining signals from the tri-state switch 18-1 to 18-3; a transmitting attenuator 13 connected with the three path coupler 15 and a duplexer 12, for adjusting a level of a transmission signal; the duplexer 12 connected with the transmitting attenuator 13, a receiving attenuator 14 and a mobile terminal 21, for assorting transmission and reception signals; the receiving attenuator 14 connected to the duplexer 12, for adjusting a level of a reception signal; a two path divider 16 connected to the receiving attenuator 14, for dividing reception signals between two paths; a three path divider 17-1 and 17-2 connected to the two path divider 16, for dividing reception signals among three paths; a tri-state switch 19-1 connected with the three path divider 17-1 and a directional coupler of a first receiving alpha antenna, for selecting one path between forward and reverse paths in a receiving step; a tri-state switch 19-2 connected with the three path divider 17-1 and the directional coupler of a first receiving beta antenna, for choosing one path between forward and reverse paths in a receiving step; a tri-state switch 19-3 connected with the three path divider 17-1 and the directional coupler of a first receiving gamma antenna, for picking up one path between forward and reverse paths in a receiving step; a tri-state switch 20-1 connected with the three path divider 17-2 and a directional coupler of a second receiving alpha antenna, for choosing one path between forward and reverse paths in a receiving step; a tri-state switch 20-2 connected with the three path divider 17-2 and the directional coupler of a second receiving beta antenna, for selecting one path between forward and reverse paths in a receiving step; and a tri-state switch 20-3 connected with the three path divider 17-2 and the directional coupler of a first receiving gamma antenna, for selecting one path between forward and reverse paths in a receiving step.
Terms such as a transmission and a reception represent herein a transmission direction of signals centering around the base station. A forward direction indicates that a signal is transmitted from the base station to an antenna, and a reverse direction signifies a transmission of a signal from an antenna to the base station.
In the test circuit of base station having such construction, for use of the conventional mobile radio communication system, the tri-state switches 18-1 to 18-3, 19-1 to 19-3 and 20-1 to 20-3 are connected with forward and reverse ports included into the directional coupler of an antenna to be tested. In such connecting construction, various tests, e.g., the call test, the hand over test, the base station's receiving sensitivity test, the voltage standing-wave ratio test, etc., are executed by using a terminal equipment.
In executing the test through a use of the test circuit of the base station in such conventional mobile radio communication system, a level of a radio frequency transmission signal or reception signal is attenuated for 3 sectors not a unit of 1 sector. Thus, it is impossible to process the radio frequency signal as an independent attenuation signal and thereby perform a mutual test between sectors. An unmanned automatic test can not be further carried out since signals of respective sectors should be separately adjusted in the construction of an existing radio frequency path adjuster.